Inorganic fillers when blended with polymers to increase the modulus of the plastics for higher engineering performance have always adversely affected toughness and processability, in particular moldability giving blemishes, streaks and other surface defects because of their incompatibility.
It has now been found, unexpectedly, that polymers differing from the basic matrix polymer, but having a solubility parameter of from about 8.5 to 13 and having some measure of compatibility with the matrix polymer can form alloys with the matrix polymer that can tolerate heavy loadings of inorganic filler. The alloys have good molding properties along with higher tensile modulus, improved heat distortion and a substantial decrease in thermal expansion providing high performance engineering polymeric alloys.